Technical Field
The present invention relates to a silver-coated conductive particles for anisotropic conductive film, anisotropic conductive paste, isotropic conductive paste and the like, and conductive paste and conductive film using the silver-coated conductive particles.
Background Art
As conductive particles for anisotropic conductive film (ACF) and anisotropic conductive paste (ACP), which are used in a liquid crystal display, a touchscreen panel or the like, there are resin particles of acryl, urethane, styrene or the like with plating of Ni, Au, or Ag.
Ag-plated resin balls can be used for the anisotropic conductive film, and can replace conductive particles in conventional isotropic conductive paste. Herewith, it is expected to reduce costs (i.e., volume is reduced to one fifth by difference in specific gravity) and to improve a handling property.
As the conductive particles above, Patent Document 1 discloses one that is manufactured by plating base particles with nickel as an undercoat and furthermore with silver. Patent Document 2 discloses one that is manufactured by plating resin powder with nickel as an undercoat and furthermore with gold, instead of silver. Especially, the one that is two-layer coated with Ni/Au is used in general as a bonding material of the anisotropic conductive such as the liquid crystal panel, the touchscreen panel, and the like.
Patent Document 3 discloses an electroless plating method of spherical crosslinked polystyrene resin or phenol resin with silver. In this electroless plating, a tin coat is formed on a surface of the spherical resin by a stannous chloride-hydrochloric acid solution; and then a silver coat is formed on the tin coat.
When it is used as conductive filler for a conductive spacer, a deformation property of filler at a pressing load on the filler and a recovery factor when the pressing load is released are required. It was required for the conductive particles described in Patent Documents 1 to 3 to improve the deformation property and the recovery factor of the filler.
Accordingly, in Patent Document 4, the present applicant suggested one that has silver-coated spherical resin having an appropriate deformation property and a recovery factor of filler and excellent conductivity, which is provided with spherical resin, a tin layer formed on a surface of the spherical resin, and silver coated on a surface of the tin layer; with an amount of silver of 2 to 80 parts by mass for 100 parts by mass of the silver-coated spherical resin, and a crystallite diameter of silver is measured at 18 to 24 nm by X-ray diffraction analysis.